// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/gfx/sequential_id_generator.h"

#include "base/logging.h"

namespace {

// Removes |key| from |first|, and |first[key]| from |second|.
template <typename T>
void Remove(uint32_t key, T* first, T* second)
{
    typename T::iterator iter = first->find(key);
    if (iter == first->end())
        return;

    uint32_t second_key = iter->second;
    first->erase(iter);

    iter = second->find(second_key);
    DCHECK(iter != second->end());
    second->erase(iter);
}

} // namespace

namespace ui {

SequentialIDGenerator::SequentialIDGenerator(uint32_t min_id)
    : min_id_(min_id)
    , min_available_id_(min_id)
{
}

SequentialIDGenerator::~SequentialIDGenerator()
{
}

uint32_t SequentialIDGenerator::GetGeneratedID(uint32_t number)
{
    IDMap::iterator find = number_to_id_.find(number);
    if (find != number_to_id_.end())
        return find->second;

    int id = GetNextAvailableID();
    number_to_id_.insert(std::make_pair(number, id));
    id_to_number_.insert(std::make_pair(id, number));
    return id;
}

bool SequentialIDGenerator::HasGeneratedIDFor(uint32_t number) const
{
    return number_to_id_.find(number) != number_to_id_.end();
}

void SequentialIDGenerator::ReleaseGeneratedID(uint32_t id)
{
    UpdateNextAvailableIDAfterRelease(id);
    Remove(id, &id_to_number_, &number_to_id_);
}

void SequentialIDGenerator::ReleaseNumber(uint32_t number)
{
    DCHECK_GT(number_to_id_.count(number), 0U);
    UpdateNextAvailableIDAfterRelease(number_to_id_[number]);
    Remove(number, &number_to_id_, &id_to_number_);
}

void SequentialIDGenerator::ResetForTest()
{
    number_to_id_.clear();
    id_to_number_.clear();
    min_available_id_ = min_id_;
}

uint32_t SequentialIDGenerator::GetNextAvailableID()
{
    const uint32_t kMaxID = 128;
    while (id_to_number_.count(min_available_id_) > 0 && min_available_id_ < kMaxID) {
        ++min_available_id_;
    }
    if (min_available_id_ >= kMaxID)
        min_available_id_ = min_id_;
    return min_available_id_;
}

void SequentialIDGenerator::UpdateNextAvailableIDAfterRelease(uint32_t id)
{
    if (id < min_available_id_) {
        min_available_id_ = id;
        DCHECK_GE(min_available_id_, min_id_);
    }
}

} // namespace ui
